1.Used to attract attention or to express doubt or warning.
多谢，天哪！用来表示感激或惊讶。
2.They express doubt that the system can work effectively.
对这种制度究竟能否奏效表示怀疑。
3.What intonation shall I use if e want to express doubt?
如果我想表示疑问我该用什么语调？
4.What intonation should I use if I want to express doubt ?
如果我想表示疑问我应该用什么语调？
5.It is used (often in brackets) to express doubt or uncertainty about a word or phrase immediately following or preceding it
问号（常在括号内）用来表示对紧接其前或其后的词或短语有疑问或无把握